- excessive load on the UMP causing it to fail to respond to browser requests in time - network issues causing a drop in the established connection between UMP and the browser - a proxy server in between UMP and the browser which is not properly set for "sticky sessions" - antivirus or network security interfering with the connection between UMP and browser - users sharing usernames/passwords, where multiple users are viewing the same page from the same location using the same username -- one user logging out may cause this error to appear for the other users who are using the same username